The present invention relates to a hydraulic lift system for use in connection with adjustable work surfaces and particularly to an improvement to the support tube for preventing leakage of hydraulic fluid.
As the work place environment changes with technology, so too do the facilities employed by companies to provide ergonomically appropriate work stations for technical, clerical, and assembly personnel. To accommodate different job tasks, frequently it is desirable to have a work surface or table which is vertically adjustable, such that the work surface can be employed by individuals of different stature and individuals in a standing position, a sitting position on a chair, or in an intermediate position when using, for example, a stool-height seat.
There exists numerous adjustable table assemblies which are either mechanically controlled by screw jack mechanisms or which are electrically controlled screw jacks. Some installations employ hydraulic cylinders with a pump for pressurizing fluid from a master cylinder to slave cylinders mounted within hydraulic lifts secured to the legs of a table for controlling the vertical adjustment of the work surface. One such system is commercially sold by Suspa Incorporated under the trademark MOVOTEC(copyright), which includes a hydraulic support tube assembly for each table leg, with each support tube assembly including an outer housing, a support tube extendable from the housing and an inner hydraulic cylinder which is coupled between the outer housing and support tube and includes a piston rod which extends and retracts for raising and lowering the support tube for extending and retracting the support tube from the housing. The support tube includes a threaded glide at its lower end which extends through a glide adapter providing an interface between the support tube and the threaded adjustable glide which is in the form of an adjustable foot which contacts the support surface for the table. In such systems, the glide adapter includes an annular outer seal extending between the inner surface of the support tube and the glide adapter to provide a sealed interface. The adjustable glide is threaded along its entire axial length to provide a maximum adjustment of the lift cylinder assembly for leveling of the table on uneven support surfaces. The piston rod from the hydraulic cylinder is typically pinned to the glide adapter, which is lockably held to the support tube by crimping. It has been discovered that with several years and thousands of cycles of use, the inner hydraulic cylinder tends to leak fluid slightly, which fluid, when exiting the hydraulic cylinder, enters the support tube area and accumulates at the lower end near the junction of the piston rod and glide adapter. With the threaded throughhole for receiving the adjustable glide, the fluid will, over a period of time, seep from the bottom of the lift, spilling over the glide and contacting the floor surface on which the table is supported. This typically only happens after several years of use, however, the result can be a hydraulic fluid stained carpet, floor, or other surface.
Thus, there exists a need to overcome this problem to prevent hydraulic fluid leakage from a hydraulic lift after years of use such that staining of the floor surface is prevented. Also, there exists a need for an improved lift cylinder which solves the leakage problem and allows the hydraulic cylinder to be removed for repair if necessary.
The system of the present invention solves this problem by providing a unique glide adapter which is relatively inexpensive and which includes a seal extending between the piston rod and glide adapter to prevent hydraulic fluid which may escape the hydraulic cylinder from seeping from the lift itself. In a preferred embodiment of the invention, the sealed glide adapter comprises a generally cylindrical member having an axially extending threaded aperture formed through one end for receiving a threaded adjustable glide. A cylindrical recess is formed in the glide adapter at an opposite end and includes an undercut recess for snap-receiving a resilient polymeric cylindrical seal which includes an annular groove for receiving an O-ring extending between the outer surface of the seal and the inner cylindrical surface of the glide adapter. The seal includes a blind aperture for receiving one end of the piston rod of the hydraulic cylinder.
With such construction, therefore, the glide adapter is sealed both on its outer periphery to the cylindrical support tube and on its inner periphery against the interior of the seal such that leakage of hydraulic fluid from the lift is prevented. These and other features, objects and advantages of the present invention will become apparent upon reading the following description thereof together with reference to the accompanying drawings.